The present invention relates to a new and useful improvement in apparatus for forming concrete members and, more particularly, to a slip-forming device for continuously pouring and forming concrete pathways such as golf cart paths, driveways, sidewalks and the like.
In the art of slip-forming concrete, a mold is employed to form the concrete aggregate to a desired shape and, as the concrete is poured and begins to settle, the mold is moved forward at a constant pace permitting the concrete to "slip" from the mold under its own weight by gravity flow. The use of such molds allows concrete members of relatively uniform shape to be continuously formed having the cross-sectional configuration of the mold. The principal advantage of slip-forming, as opposed to more conventional concrete-forming methods, is that it eliminates the costly labor and materials necessary to construct, assemble and dismantle wooden or metal forms which normally are required to restrain the sides of the concrete after pouring.
A critical problem with prior art slip-forming devices used in the construction of concrete pathways is that the concrete that is discharged from such devices tends to crack or fracture, particularly at the outside edges, shortly after the pouring and forming operations. The tendency to crack during setting is particularly acute in applications requiring a concrete aggregate that contains an amount of water sufficient to ensure the formation of a smooth surface as the concrete member is being discharged from the form. The cracking problem associated with such pathways also appears to be more severe in climates having high temperatures and relatively low humidities such as those in the southwestern part of the United States. Frequently, an entire concrete section must be removed and repoured due to the cracking and/or fragmentation following setting.
Although it is known that chemical or oil-base curing agents may be applied to hand-formed concrete members following pouring in order to minimize cracking, such agents are relatively ineffective in slip-forming operations and add to the overall cost per foot of concrete construction. Thus, concrete pathways formed using prior art slip-forming devices invariably must be hand-finished for resurfaced using conventional hand trowelling or finishing equipment in order to provide a uniform, smooth surface or to eliminate cracks forming during setting. The additional cost in labor and materials necessary to complete such refinishing operations has made concrete far less economical as a construction medium for golf cart paths, driveways and other flat or crowned surfaces which do not require steel reinforcing.
One solution to the cracking problem which has been adopted by prior art devices is to lower the water-to-cement ratio of the aggregate while employing means to vigorously vibrate or agitate the concrete mix prior to and immediately after the initial pour. Such agitation techniques have been somewhat successful in allowing for the formation of a smooth surface while avoiding the cracking problems attendant non-vibration slip-forming apparatus. However, in addition to their increased expense, complexity and maintenance requirements, such devices are often considered less desirable than hand-forming operations due to their inherent lack of consistency and because of the increased wear resulting from the use of auxiliary vibration apparatus during the pouring operation. In addition, such devices do not lend themselves to applications requiring frequent changes in direction such as, for example, in the formation of golf cart paths. Typical prior art devices exhibiting such deficiencies are disclosed in U.S. Pat. Nos. 3,954,359, 3,468,001, 4,027,990, 3,423,492, and 2,664,794.
Thus, although it is known that vibration in combination with means for compression of the concrete will facilitate the formation of a smooth surface, the prior art techniques requiring vibration present quality control and efficiency problems which continue to plague the concrete art.
It has now been found that the recurring problems of cracking and deterioration associated with conventional slip-forming devices may be eliminated by a unique design configuration for a slip-forming mold which allows for the removal of vibration means altogether. In particular, it has been discovered that a specific combination of weight and design features will allow the aggregate to be continuously compressed, settled and smoothed without requiring auxiliary vibration apparatus. It has also been found that a certain consistency of concrete aggregate used in the method according to the invention tends to reduce the possibility of cracking or fracture, while ensuring that the finished members are formed having a uniform thickness and smooth surface.
The slip-form apparatus constructed in accordance with the present invention ensures that the formed concrete aggregate will not require subsequent hand trowelling, finishing, or curing operations and thus permits a substantial reduction in the cost of producing concrete pathways. It also eliminates any need to construct conventional metal or wooden forms prior to pouring.
Accordingly, it is an object of the present invention to provide for a concrete slip-forming device which will allow for the formation of concrete members having substantially uniform thickness and smooth surfaces while ensuring that such members will not crack or deteriorate during setting. It is a further object of the invention to provide a slip form which will allow concrete pathways to be continuously formed without additional hand trowelling, finishing or curing operations following the initial pour. It is still another object of the present invention to provide a method for continuously forming concrete pathways which will not crack or deteriorate and which do not require conventional vibration means.
Finally, it is an object of the present invention to provide a method for forming concrete pathways that is considerably more cost-efficient and economical than conventional prior art techniques.
Other features, objects and advantages of the subject invention will appear more fully from the following description of illustrative embodiments taken in conjunction with the appended drawings.